Cliffs51

Recently purchased 07 2.4 1LT. on a 100 mile round trip the check engine light came on. Codes were PO121 PO300 and P1174. I had planned on changing plugs and air filter anyway since I didnt know their condition. This morning I changed them. The plugs didnt look awful and they all looked about the same. The air filter was a little dirty. The plugs were AC Delco and I replaced them with the same. I did find that the outside air intake duct tube was cracjed open and had been taped thus letting hot underhood air into the intake. (I suspect that was causing the codes). Unfortunately I also had to use duct tape to fix it until I can find a permanent fix. Started the car up when I was done and no check engine light. 😁

Cat Man HHR

The intake hose really isn't a problem other than the hot air into the air filter.
There are easy ways to fix that along with the Red Green tape fix, which you did, lol.
How many miles on your car?
The P0300 (random misfire) and P1174 (injector problem) might be related and by you changing a "bad" spark plug have fixed that.
The P0121 for a throttle body problem is something I'm sure someone will chime in about.

donbrew

Nope, those codes are more likely the MAF sensor was loose. Hot air doesn't make that much difference.

BTW, that's Pzero121.

Oldblue

Woolly worm fix, flexible dryer tube





This worked for an extra air intake to my stock air box.

Cat Man HHR

By loose, do you mean the clamps that hold it? Allowing air to leak passed it, causing the code?

Cliffs51

Car has 160k miles. MAF was not loose. I like the dryer vent idea 😁

Cliffs51

I did all of the service with the MAF sensor left in place. Saves having to disconnect the battery. Ill post pics if the spark plugs later today

Cat Man HHR

I know this might sound stupid, but since the 2.2 and 2.4 have just a vent hose from valve cover to inlet of throttle body, maybe just maybe, R&I the throttle body and clean it. With the amount of miles on the engine, it can't hurt.

donbrew

No, I meant the connector. No need to mess with the battery, just turn the key off. The wires may have gotten yanked or it just wasn't plugged in good.

All of the codes are related to calculation based on A/F. P1174 says that one of the cylinders was lean, P0300 says yes but it was so quick I couldn't tell which one, P0121 says "ooh ooh something is reporting too much air, that's why".

P0121 means that the calculated airflow is not equal to the actual airflow, so either there is too much air or a sensor thinks there is. Like a loose connection/broken wire. QED

Cliffs51

I fully intend to remove and clean the throttle body, just havent had time yet. From the looks of the dirt etc. on it I dont think its ever been taken off and cleaned. Not gonna happen for a week or two though because I start my monthly magazine delivery Thursday and I will be using the HHR for that.